It has been suggested that a computer is a thermodynamic engine that sucks entropy out of data, turns that entropy into heat, and dumps the heat into the environment. The ability of prior art thermal management technology to get that waste heat out of semiconductor circuits and into the environment, at a reasonable cost, limits the density and clock speed of electronic systems.
A typical characteristic of heat transfer devices for electronic systems is that a semiconductor chip often thermally contacts a passive heat spreader plate, which conducts the heat from the chip to the evaporator of one of several types heat transfer devices, and then on into the atmosphere. As the power to be dissipated by semiconductor devices increases with time, a problem arises: over time the thermal conductivity of the available materials becomes too low to conduct the heat from the semiconductor device to the atmosphere with an acceptably low temperature drop. The thermal power density emerging from the semiconductor devices will be so high that even copper or silver spreader plates will not be adequate.
Thermal energy can sometimes be transported by an intermediate loop of recirculating fluid; heat from the hot object is conducted into a heat transfer fluid, the fluid is pumped by some means to a different location, and there the heat is conducted out of the fluid into the atmosphere. For example, thermosyphons use a change in density of the heat transfer fluid to impel circulation of the fluid, while heat pipes and boiling fluorocarbons use a phase transition in the heat transfer fluid to impel circulation of the fluid. While these approaches have important cooling applications, their cost for implementation will have to be reduced to generally impact semiconductor cooling.
Another technology that has proven beneficial is the heat pipe. A heat pipe includes a sealed envelope that defines an internal chamber containing a capillary wick and a working fluid capable of having both a liquid phase and a vapor phase within a desired range of operating temperatures. When one portion of the chamber is exposed to relatively high temperature it functions as an evaporator section. The working fluid is vaporized in the evaporator section causing a slight pressure increase forcing the vapor to a relatively lower temperature section of the chamber, defined as a condenser section. The vapor is condensed in the condenser section and returns through the capillary wick to the evaporator section by capillary pumping action. Because a heat pipe operates on the principle of phase changes rather than on the principles of conduction or convection, a heat pipe is theoretically capable of transferring heat at a much higher rate than conventional heat transfer systems. Consequently, heat pipes have been utilized to cool various types of high heat-producing apparatus, such as electronic equipment (See, e.g., U.S. Pat. Nos. 5,884,693, 5,890,371, and 6,076,595).
Electronic systems must not only be cooled during their working life, but also during initial packaging, and testing prior to use in a commercial product. In many testing applications, the tests must be performed at elevated temperatures. Automated test systems are commonly outfitted with temperature control systems which can control the temperature of the device or devices under test. For example, and referring to FIG. 5, a semiconductor device test system A often includes a temperature-controlled semiconductor device support platform B that is mounted on a prober stage C of prober station D. A top surface E of the device support platform B supports a semiconductor device F and incorporates conventional vacuum line openings and grooves G facilitating secure holding of semiconductor device F in position on top surface E of device support platform B. A system controller is provided to control the temperature of device support platform B. A cooling system I is provided to help regulate the temperature of device support platform B. A user interface is provided in the form of a touch-screen display J where, for example, a desired temperature for the top of support platform B can be input. Temperature controlled systems for testing semiconductor devices during burn-in are well known, as disclosed in the following patents which are hereby incorporated by herein by reference: U.S. Pat. Nos. 4,037,830, 4,213,698, RE31053, U.S. Pat. Nos. 4,551,192, 4,609,037, 4,784,213, 5,001,423, 5,084,671, 5,382,311, 5,383,971, 5,435,379, 5,458,687, 5,460,684, 5,474,877, 5,478,609, 5,534,073, 5,588,827, 5,610,529, 5,663,653, 5,721,090, 5,730,803, 5,738,165, 5,762,714, 5,820,723, 5,830,808, 5,885,353, 5,904,776, 5,904,779, 5,958,140, 6,032,724, 6,037,793, 6,073,681, 6,245,202, 6,313,649, 6,394,797, 6,471,913, 6,583,638, and 6,771,086.
None of the foregoing technologies or devices has proved to be entirely satisfactory.